Biomedical electrode and method for its manufacture

ABSTRACT

A biomedical electrode comprises a connector stud ( 1 ) anchored in a patch of adhesive-coated backing material ( 7 ) which is used to secure the electrode to the skin of a patient. The connector stud ( 1 ), which is located in a pierced opening in the backing material ( 7 ), has a head portion ( 2 ) to which an electrical lead of an electromedical monitoring/diagnostic system can be attached, and an electrode plate ( 3 ) which, when the biomedical electrode is in use, is placed in electrical communication with the skin of the patient. A strip of ionically-conductive adhesive ( 9 ) extends across the backing material and over the electrode plate ( 3 ) and a strip of scrim material ( 17 ) is located adjacent the adhesive coating on the backing material, underneath the adhesive strip ( 9 ). The two strips ( 9, 17 ) are displaced, relative to the electrode plate ( 3 ), towards a tab ( 13 ) which is used for removing the electrode from the skin of the patient.

FIELD OF THE INVENTION

The present invention relates to biomedical electrodes, that iselectrodes which can be attached to the skin of a patient to establishan electrical connection between the skin and an electromedicalmonitoring/diagnostic/therapeutic system. The invention relates moreespecially, but not exclusively, to ECG electrodes for use in a part ofa system for monitoring and/or diagnosing cardiac function and islikewise applicable to electrodes for use in electroencephalograph (EEG)systems.

BACKGROUND OF THE INVENTION

ECG monitoring systems are well known and are used in a variety ofhealth care situations. Such systems require the use of electrodes whichare attached to the skin, at selected points of the body, to enableelectrical signals (indicative of cardiac function) to be fed to anelectrocardiograph. The electrodes, which are conventionally attached tothe skin by an adhesive, are required to make good electrical contactwith the skin and to be constructed to permit the easy attachment ofelectrical leads from the electrocardiograph. It is also desirable thatthe electrodes should be easy to remove from the protective linermaterial with which they are normally provided and from the skin of apatient, after use, without leaving any adhesive or other residues.

One known type of ECG electrode comprises a connector stud having a headportion to which electrical leads can be attached, and an electrodeplate through which contact is made to the skin. The stud is located ina patch of backing material, with the electrode plate positioned on oneside of the material and the head portion on the other. The side of thebacking material on which the electrode plate is positioned is coatedwith an adhesive. enabling the ECG electrode to be securely attached tothe skin and an electrical contact to be formed between the skin and theelectrode plate. To improve the electrical connection between the skinand the electrode plate. the latter may, for example, be coated with alayer of an ionically-conductive paste, cream or gel, or covered with alayer of sponge material in which an ionically-conductive gel isembedded.

Connector studs which are formed in two parts, designed to snaptogether, are known. One part of the stud provides the electrode plateand the other part provides the head portion and, during the process ofassembling the electrode, the two parts are located on opposite sides ofthe backing material and snapped together, thereby clamping the backingmaterial between them. The connector stud is thus well anchored in thebacking material so that the likelihood of it separating from thebacking material when the electrode is in use is comparatively low.However, the two-part construction of the stud increases the complexityof the assembly process.

Biomedical electrodes with one-piece connector studs are also known.U.S. Pat. No. 4 352 359, for example, describes an electrode in whichthe connector stud is a one-piece stud, the head portion of which islocated in a punched aperture in a patch of adhesive tape. The adhesivetape overlies the upper surface of the electrode stud and aids inholding the electrode securely to the skin of a patient. In anotherknown electrode which employs a one-piece stud, the backing material isa comparatively thick foam material and an integral flange is providedin the stud at a distance from the electrode plate so that it willoverlie the upper surface of the backing material. Additional shaping inthe form of a smaller flange is provided on the stud between the flangeand the electrode plate. The stud is located in a punched aperture inthe backing material with the additional shaping on the stud thus beinglocated within the aperture.

The use of one-piece connector studs reduces the number of componentsrequired to assemble a biomedical electrode but can increase thelikelihood of the stud separating from the backing material,particularly when electrical leads are being attached to the stud.Alternatively, if the connector stud is shaped so that it is less likelyto separate from the backing material, the insertion of the stud intothe backing material during the assembly process can become moredifficult.

U.S. Pat. No. 4 640 289 describes a biomedical electrode with aone-piece terminal member located in a punched aperture in a piece ofadhesive, in which a retainer sheet is provided to prevent the terminalmember separating from the remainder of the electrode. An automatedmethod for producing the electrode is also described. The adhesivesurface of the electrode is protected by a release liner and, tofacilitate removal of the electrode from the release liner and, afteruse, from the skin of the patient, the electrode is provided with a tabformed in a margin of the adhesive tape.

U.S. Pat. Nos. 3,841,312 and 4,117,846 describe biomedical electrodes inwhich a separate ring or washer is employed to ensure that the connectorstud is well anchored in a backing material.

SUMMARY OF THE INVENTION

The problem with which the present invention is concerned is that ofenabling biomedical electrodes to be produced more simply and in a lesscostly manner without adversely affecting their reliability andconvenience when in use.

The present invention provides a biomedical electrode comprising abacking material coated on one side with a pressure-sensitive adhesiveand having a non-adhesive margin to facilitate the handling of theelectrode; a connector stud located in the backing material, the studhaving an electrode plate located on one side of the backing materialfor electrical connection to the skin of a patient and, on the otherside of the backing material, a head portion to which an electricalconnector can be attached; a strip of ionically-conductive adhesiveextending, generally parallel to the non-adhesive margin, across theadhesive-coated side of the backing material and over the electrodeplate of the stud; and a parallel strip of scrim material located at theinterface of the ionically-conductive and pressure-sensitive adhesive;the strip of scrim material being displaced, relative to the electrodeplate of the stud, towards the non-adhesive margin of the backingmaterial and the edges of both strips nearest to the non-adhesive marginbeing positioned to one side of the electrode plate.

In one embodiment, the connector stud is one piece. In anotherembodiment, the connector stud comprises two pieces.

The invention further provides a biomedical electrode comprising abacking material coated on one side with a pressure-sensitive adhesiveand having an adhesive-free margin to facilitate the handling of theelectrode; a connector stud located in the backing material, the studhaving an electrode plate located on one side of the backing materialfor electrical connection to the skin of the patient and, on the otherside of the backing material, a head portion to which an electricalconnector can be attached; and a strip of ionically-conductive adhesiveextending across the adhesive-coated side of the backing material andover the electrode plate.

The present invention also provides a biomedical electrode comprising abacking material securable by an adhesive to the skin of a patient, anda connector stud located in a pierced opening in the backing material,the stud having an electrode plate located on one side of the backingmaterial for electrical connection to the skin of the patient and, onthe other side of the material, a head portion to which an electricalconnector can be attached.

A method of manufacturing a biomedical electrode, comprising the stepsof providing a connector stud comprising an electrode plate forelectrical connection to the skin of a patient and a head portion; andinserting the connector stud into a pierced opening in a backingmaterial, to locate the stud in the backing material with the electrodeplate and the head portion on opposite sides of the material.

The present invention also provides a method of manufacturing abiomedical electrode, comprising the steps of forming an opening in abacking material; inserting a tubular member through the opening fromone side of the backing material; providing a connector stud comprisingan electrode plate for electrical connection to the skin of a patient,and a head portion; locating the stud, head portion first, in the end ofthe tubular member from the other side of the backing material.

By way of example only, embodiments of the invention will be describedwith reference to the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a connector stud for an ECG/EEGelectrode, in accordance with the invention;

FIG. 2 shows a longitudinal cross-section on an enlarged scale throughthe stud of FIG. 1;

FIG. 3 is a perspective view, from above, of an ECG electrodeincorporating the stud of FIGS. 1 and 2;

FIG. 4 is a view from below of the electrode shown in FIG. 3;

FIG. 5 is an enlarged, diagrammatic end view in the direction of thearrow V in FIG. 4;

FIG. 6 shows an enlarged, diagrammatic, cross-section on the line VI—VIin FIG. 4;

FIG. 7 is a view, similar to FIG. 4, of an alternative form ofelectrode;

FIG. 8 illustrates, schematically, a process for the production ofelectrodes as shown in FIGS. 3 to 6;

FIG. 9 illustrates, schematically, the insertion of connector studs intobacking material in the process illustrated in FIG. 8;

FIG. 10 illustrates apparatus for carrying out the process illustratedin FIG. 9;

FIG. 11 is a view, similar to FIG. 6 of yet another form of electrode;and

FIG. 12 illustrates apparatus for carrying out the process of analternative embodiment.

EMBODIMENTS OF THE INVENTION

The connector stud 1 shown in FIGS. 1 and 2 is a one-piece mouldedcomponent comprising: a rounded head portion 2; a circular electrodeplate 3 at the base of the stud; an outwardly projecting circular flange4 which extends completely around the head portion 2 at the base of thelatter; and, between the electrode plate 3 and the flange 4, a stemportion 5. The stem portion 5 is smooth, as can be seen from FIG. 2, sothat the space 6 between the electrode plate and the flange isuninterrupted by any projections from the stem portion 5.

When in use in a biomedical electrode as described below, the bottomsurface of the electrode plate 3 of the stud is placed in electricalcommunication with the skin of a patient and the stud 1 will thenprovide an electrical connection between the patient's skin and the headportion 2 of the stud, to which one lead of an electromedicalmonitoring/diagnostic system is connected. To enable the connector studto be held in contact with the patient's skin, the stud is anchored in apiece of adhesive-coated backing material which is located, as will bedescribed below, in the space 6 between the electrode plate 3 and theflange 4.

The stud 1 is preferably formed of a plastics material, for example aglass-filled copolymer of acrylonitrile, butadiene and styrene (ABS),with a coating 1 a of an electrically-conductive material, for examplesilver/silver chloride. It may, however, be formed of any other materialknown to be suitable for the connector studs of biomedical electrodes,for example stainless steel or aluminium.

Typically, the diameter of the electrode plate 3 is about 10.15 mm; themaximum transverse dimension of the head portion is about 3.8 mm; thediameter of the flange 4 is about 6.0 mm; the diameter of the stem isabout 2.45 mm; the height of the stud 1 is about 6.0 mm and the width ofthe space 6 is about 1.1 mm.

An ECG electrode incorporating the stud 1 is shown in FIGS. 3 to 6. Thestud 1 is positioned in an opening (not visible in FIGS. 3 to 5) in thecentre of a generally square patch of non-conductive backing material 7,with the backing material being held in the space 6 in the stud. In thatway, the stud 1 is anchored in the backing material 7 with the electrodeplate 3 located on one side of the material, and the flange 4 and headportion 2 located on the other. As will be described in greater detailbelow, the opening in the backing material (in which the stud 1 islocated) is preferably a pierced opening but it could, alternatively, bea punched opening.

The backing material 7 is typically a synthetic foam material, forexample a 1 mm thick polyethylene foam film, about 34 mm×37 mm withrounded corners and, along one side, an extension 14 with a curved edge.The rear surface of the backing material 7 is provided with an adhesivecoating comprising a pressure-sensitive adhesive 8 (which adhesive ispreferably biocompatible with mammalian skin) over which is a strip 9 ofan ionically-conductive adhesive which extends across the patch ofbacking material from one edge to the other, parallel to the side withthe extension 14. The ionically-conductive adhesive covers the bottomsurface of the electrode plate 3 of the stud and leaves two outer stripsof the pressure-sensitive adhesive exposed. The central strip 9 ofionically-conductive adhesive is typically about 13.2 mm wide and, asshown in FIGS. 4 to 6, is displaced relative to the electrode plate 3towards the extension 14, so that the edge 15 of the strip nearest tothe extension 14 is located to one side of the electrode plate and theother edge 16 just touches the edge of the electrode plate.

To ensure good adhesion of the strip 9 of ionically-conductive adhesiveto the backing material 7, a strip 17 of scrim material (not visible inFIG. 4) is located between the adhesive strip 9 and thepressure-sensitive adhesive 8 on the backing material. The scrimmaterial is co-extensive with the adhesive strip 9 but, as shown in FIG.6, is positioned on the other side of the electrode plate 3 (i.e.immediately adjacent the pressure-sensitive adhesive 8).

The adhesive coatings 8, 9 on the backing material are protected duringstorage until use by a removable liner 10 (shown as being transparent)which may be formed from any suitable material, for example asiliconized polyester film having a thickness of about 0.05 mm. A tabmaterial 13 is located over the pressure-sensitive adhesive 8 on theextension 14 of the backing material 7, and remains in place to assistin removing the electrode from the liner 10 and also in removing theelectrode, after use, from the skin of a patient. The tab material 13may be formed from any suitable material, for example paper or polyesterfilm and it may be coloured if desired.

The upper surface of the backing material 7 is covered by a label 18 ofany suitable material, for example siliconized polyethylene, which may,if desired, be coloured or carry printed information. Adjacent the stud1, the label 18 extends with the backing material into the gap 6 betweenthe flange 4 and the electrode plate 3.

To ensure that the stud 1 will be well anchored in the backing material7, the diameter of the flange 4 is preferably at least 1.3 (morepreferably 1.5) times the maximum transverse dimension of the headportion 2. A process by which a connector stud 1 having a flange 4 ofthat size can be inserted into the backing material 7, and be wellanchored, will be described below.

The pressure-sensitive adhesive 8 on the electrode backing material 7can be any appropriate pressure-sensitive adhesive known to be suitablefor use on biomedical electrodes. Suitable adhesives include acrylateester adhesives, and more particularly acrylate ester copolymeradhesives. Such adhesives are generally described in U.S. Pat. Nos.2,973,826; Re 24,906; Re 33,353; 3,389,827; 4,112,213; 4,310,509;4,323,557; 4,732,808; 4,917,928; 4,917,929; and European PatentPublication 0,051,935.

The ionically-conductive adhesive 9 on the electrode backing material 7can be any appropriate ionically-conductive adhesive known to besuitable for use on biomedical electrodes. Ionically-conductiveadhesives useful in connection with biomedical electrodes are describedin U.S. Pat. Nos. 4,524,087; 4,539,996; 4,848,353; 5,133,356; 5,225,473;5,276,079; 5,338,490; 5,362,420; 5,385,679; and WO-A-95/20634 andWO-A-94/12585.

The strip of ionically-conductive adhesive 9 may be coated, either in aflood coating or in a pattern coating, onto the backing material 7 andthen cured. If using a pattern coating, use of the process disclosed inPCT Patent Publication WO96/15715 can be used. Alternatively, asdescribed below, the adhesive may be pre-cured and a strip of thepre-cured adhesive may be laminated to the backing material.

From the point of view of economy, the strips of ionically-conductiveadhesive 9 and scrim material 17 are advantageously as narrow aspossible consistent with reliability and with ensuring adequateelectrical contact between the electrode plate and the skin of thepatient. In the case of the electrode shown in FIGS. 3 to 6, that isachieved by arranging that the width of strips 9, 17 is such that thestrips extend beyond the electrode plate 3 only on the side nearest thetab 13, 14 and then only by a very small amount (typically about 2 mm),just sufficient to ensure that the scrim material 17 can maintain thebond between the ionically-conductive adhesive 9 and thepressure-sensitive material 8 in the vicinity of the electrode plate 3particularly when the electrode is removed either from the linermaterial 10 or, after use, from the patient's skin using the tab 13, 14.

In some cases. however, further economy can be achieved by reducing thewidth of the scrim material 17 still further and FIG. 7 is a view,similar to FIG. 4, illustrating how that can be done. In the electrodeof FIG. 7, the scrim strip (the position of which is indicated by theshaded portion 19) has a width corresponding to the distance between theedge 15 of the conductive adhesive strip 9 and the nearest part of theelectrode plate 3. A scrim strip which is slightly wider thanillustrated in FIG. 7 could also be used and could be arranged to extendover, rather than under, the electrode plate 3 (i.e. adjacent theadhesive strip 9) provided that it is not so wide that it would impairthe electrical connection between the adhesive strip 9 and the electrodeplate 3.

The arrangement illustrated in FIG. 7 enables a reduced amount of scrimmaterial to be used while ensuring that the ionically-conductiveadhesive 9 remains well adhered to the backing material 7 and is notpulled away from the backing material when the electrode is removedeither from the liner material 9 or, after use, from the patient's skinusing the tab 13.

In the case of the electrode illustrated in FIGS. 3 to 6, the strip ofscrim material is applied to the backing material 7 before the connectorstud 1 is inserted. In the case of the electrode of FIG. 7, the scrimmaterial can be applied to the backing material either before or afterthe connector stud 1 is inserted.

The non-conductive backing material 7 of the electrode can be anyappropriate material, of any suitable thickness and shape (e.g. round.oval, rectangular). When the material is polyethylene foam, the mostsuitable thicknesses are within the range of from 0.75 to 1.5 mm. Othersuitable materials, apart from the polyethylene foam described aboveinclude polyester non-woven materials, cellulose rayon non-wovenmaterials, and polyethylene vinyl acetate films. When backing materialis used which has a different thickness from the backing material 7 ofFIGS. 3 to 6, the distance between the base 3 and the flange 4 of theconnector stud 1 should be increased or decreased accordingly.

A process for producing electrodes as shown in FIGS. 3 to 6 will now bedescribed with reference to FIG. 8. The process preferably comprises thefollowing steps:

(i) A continuous strip of electrode backing material 19, laminated withlabel material 22 on one side and coated with a pressure-sensitiveadhesive on the other side, is fed through a laminating station 20 inwhich a continuous strip of scrim material is 26 is laminated to theadhesive, in a location corresponding to the intended location of thescrim in the finished electrode. The backing material 19 fed to thestation 20 also carries a narrow strip of tab material along one edge ina location corresponding to the tab material 13 in the finishedelectrode.

(ii) The backing material 19 is then fed to a stud insertion station 21,described in greater detail below, in which spaced connector studs areanchored in the scrim material.

(iii) The backing material 19 is then fed to a laminating station 23 inwhich a strip 24 of pre-cured ionically-conductive adhesive laminated tothe liner material 25 for the finished product is applied over the scrimmaterial and the line of connector studs.

(iv) The final laminated assembly, comprising backing material, scrim,connector studs, adhesives, tab material and product liner is then fedto a final cutting station 29, in which it is cut into individualelectrodes.

The waste material is then removed, as indicated at 30.

The process described above can, if required, be carried out in such away that two, or more, rows of electrodes are produced simultaneouslyacross the width of the backing material 19.

The manner in which the connector studs are inserted into the backingmaterial in the station 21 of FIG. 8 will now be described withreference to FIGS. 9 and 10. The backing material 19, with the strip ofscrim material, passes over a piercing head 31 comprising a piercingtool 32 surrounded by a tubular sleeve 33. The adhesive-coated side ofthe backing material is uppermost as seen in FIG. 9 (i.e. it is the sideremote from the piercing head 31). In steps (a) and (b), the piercingtool 32 is pushed through the backing material 19 and scrim. In step(c), the sleeve 33 is pushed through the pierced opening 34 in thebacking material and holds it open while the piercing tool is withdrawn.

Subsequently, in steps (d) to (g), a connector stud 35 is placed (headportion first) into the end of the tubular sleeve 33 and is held inplace, with the flange 4 of the stud engaging the end of the sleeve, asthe latter is withdrawn through the opening 34. The stud is thenreleased, in step (h) when it has reached the position in which theedges of the pierced opening are located in the space 6 (FIGS. 1 and 2)between the electrode plate 3 and the flange 4 of the stud. The backingmaterial then passes to the station 23 of FIG. 8.

To prevent the connector studs 35 slipping too far into the tubularsleeve 33, the flange 4 of each stud should have a diameter greater thanthat of the sleeve. To enable the backing material 19 to lie flat aroundthe stem 5 of each stud, the stem 5 should have as small a diameter aspossible, preferably not more than 0.75 times that of the flange 4.

Advantageously, the process illustrated in FIG. 9 is carried outcontinuously in the manner illustrated in FIG. 10. The backing material19 with scrim passes over a continuously-driven insertion wheel 40containing a plurality of radially-located piercing tools 32 andsurrounding tubular sleeves 33. The piercing tools and sleeves 32, 33are cam driven so that they each move uniformly in and out of theinsertion wheel 40 in the manner illustrated in FIG. 9. The backingmaterial 19 is initially held against the insertion wheel 40 by a firstbelt 41 while the pierced openings are being formed. Connector studs 1to be placed on the ends of the sleeves 33 are then fed into position at42 and held in place by a second belt 43 as the sleeves are withdrawn tolocate the studs in the backing material 19 which is then removed asindicated at 44.

A pre-cured conductive adhesive for use in step (iii) of the processdescribed above with reference to FIG. 8 can be prepared according tothe following procedure. A precursor is prepared, having the followingformulation (by weight): 18.61% acrylic acid; 0.05%2,2-dimethoxy-2-phenyl acetophenone; 0.09% 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-methylpropyl)ketone; 0.04% methylenebis(acrylamine); 41.39% glycerine; 21.35% deionized water; 0.09% guargum; 16.53% NaOH (50% sol); 1.85% potassium chloride. The precursor canbe prepared in the following manner: A kettle equipped with overheadstirrer and a cooling jacket is charged with the acrylic acid,2,2-demethoxy-2-phenyl acetophenone,4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-methylpropyl)ketone, methylenebis(acrylamide), glycerin, guar gum, and a proportion of the deionizedwater. To the well stirred solution is charged the 50% aqueous NaOHportionwise maintaining the batch temperature below 38° C. The hydroxideline is rinsed with deionized water and stirred. and the potassiumchloride is then added as a 25% aqueous solution (preferably warmed to atemperature of about 80-90° F. (26 to 32° C.)) to yield a coater-readyprecursor. The precursor is coated onto a siliconized polyester liner at0.25 mm thick, overlaminated with a siliconized polyester liner, andpassed through a curing chamber consisting of banks of fluorescent“black” lights, exposing the material to an intensity of 1.0 mW/sqcm anda total dose of 315 mJ/sqcm. Following removal of one of the polyesterliners, the cured conductive adhesive so prepared is ready for usetogether with the final product liner in the laminating station 23 ofFIG. 8.

To facilitate the handling of the cured adhesive and, if necessary,enable it to be transported from the location in which it is cured, ascrim material may be located on the liner material onto which theadhesive precursor is coated. Following curing, the scrim material willbe embedded substantially in the middle of the adhesive layer.

A tubular sleeve, similar to the sleeve 33 of FIG. 9, can also be usedwhen it is required to insert a stud of the type shown in FIGS. 1 and 2into a punched (rather than pierced) hole in electrode backing material7 and will facilitate the location of the stud in the hole, despite thecomparatively large diameter of the flange 4 of the stud 1. When thestud is in position in the backing material, the comparatively largediameter of the flange 4 again ensures that the stud is well anchored inthe backing material 7.

It will be appreciated that, although a continuous process asillustrated in FIGS. 9 and 10 is preferred in that it enables a fastproduction rate to be achieved (and the cost of producing electrodes tobe reduced), it is not essential since the same process could be carriedout intermittently.

It will also be appreciated that the process could be used to produceelectrodes having a different form from that shown in FIG. 3. Forexample, the overall shape of the connector studs 1 could be varied, ascould the shape of the patches 7 of backing material. In addition,individual features of the process could be applied to the production ofother forms of electrodes. For example, the step 23 (FIG. 8) oflaminating a strip of pre-cured conductive adhesive with liner materialto the backing material could be used in the production of many othertypes of biomedical electrodes, including electrodes which do notincorporate a connector stud. More specifically, strips of precuredconductive adhesive could be used in biomedical electrodes of the typewhich comprise a patch of an ionically-conductive material which issecured directly to the skin and to which an electrical lead of anelectromedical monitoring/ diagnostic/ therapeutic system can beattached. In that case, a strip of pre-cured adhesive could be laminatedacross the rear surface of the patch of ionically-conductive material.

A process similar to that illustrated in FIG. 8 could be used to produceelectrodes of the type illustrated in FIG. 7. Alternatively, the processcould be modified so that the scrim material is applied to the backingmaterial after the connector studs have been inserted, but before theionically-conductive adhesive is applied.

As a further alternative, the backing material 19 supplied to thelaminating station 20 can be strip coated with the pressure-sensitiveadhesive so that it has an adhesive-free margin along the side at whichthe tab 14 will be located in the final product. In that case, thematerial for the tab 13 is omitted but the label material on the otherside may be distinctively marked (e.g. coloured) along that margin. Theremainder of the process remains unchanged and the finished electrodewill be the same as that shown in either FIG. 4 or FIG. 7 except thatthere will be no tab material 13 and the tab will, instead, be formedsimply by the adhesive-free margin of the backing material with thelabel material on the upper surface of the electrode. In that way,further economies can be achieved because the material for the tab 13 isnot required and less adhesive is used. The strip coating of thepressure-sensitive adhesive can be applied to a full width of backingmaterial which is then slit into suitable widths for the process of FIG.8. Advantageously, the width of backing material used in the process ofFIG. 8 allows two electrodes to be formed side-by-side, in which casethere would be an adhesive-free margin along each edge (typically about5.0 mm wide) with a band of pressure-sensitive adhesive (about 60.5 mmwide between. In that case the full width of backing material would bestrip coated with several parallel pressure-sensitive adhesive bands,each 60.5 mm wide, separated by adhesive free bands having a width of 10mm. with 5.0 mm wide adhesive-free margins along each edge of thematerial. The full-width material would then be slit longitudinally atthe mid-point of each adhesive free band. The full-width backingmaterial could, if desired, be laminated with full-width label materialwhich could carry tab-identifying printed stripes in locationscorresponding to the adhesive-free bands on the backing material.Advantageously, the tab-identifying stripes are slightly wider than theadhesive-free bands (typically 12.0 mm wide).

An electrode produced according to the method just described isillustrated in FIG. 11. The electrode is generally similar to that shownin FIG. 7 in that the width of the scrim material 17 is such that itextends only between the edge 15 of the adhesive strip 9 and the nearestpart of the electrode plate 3. Corresponding parts of the electrodecarry the same references as in FIG. 7. The tab portion 14 of thebacking material 7 is free of adhesive and the overlying region 18 a ofthe electrode label 18 is coloured to enable the tab to be readilyidentified.

Strip coating of adhesive material as used to produce the electrodeshown in FIG. 11 is well known and need not be described in detail here.The use of strip coating in the production of biomedical electrodes isdescribed, for example, in WO96/15715.

An alternative embodiment to the electrode shown in FIG. 11 is anelectrode comprising two pieces for the connector stud 1, a stud pieceand an eyelet piece. It is known to those skilled in the art that aconnector is more typically comprised of these two pieces, such as thosestud/eyelet connectors used in the manufacture of 3M Red Dot™ biomedicalelectrodes by Minnesota Mining and Manufacturing Company (3M) of St.Paul, Minn. USA. Any of the stud/eyelet materials used in thesecommercial electrodes can be used in the process of the presentinvention. Manufacturing of a two-piece connector stud involves somealteration to the equipment shown in FIG. 10. FIG. 12 shows theapparatus useful for forming an electrode of the present invention thatcontains a two-piece connector stud.

A wheel 50 is the same as the wheel 40 shown in FIG. 10. Into backingmaterial 19 moving along wheel 50, studs coming from direction 52 areinserted at junction 53 by the method described above for the singlepiece connector stud 1. The backing material 19, with studs therein,then passes to the wheel 54 at location 55 where the studs 52 arepositioned ready to receive the eyelets at junction 56, fed in on wheel57 from a line feeder from direction 58. The eyelets are pushed onto thestuds at junction 56 between wheels 54 and 57. The backing material 19is trapped between the studs and the eyelets and proceeds in assembledform along wheel 57 in direction 59.

Suitably-shaped and sized electrodes of the general type shown in FIGS.3 to 6, 7 and 11, and described in FIG. 12 can be also used inassociation with EEG systems. Likewise, biomedical electrodes of thepresent invention can be connected electrically and mechanically toelectrosurgical generators or cardiac stimulation devices to providedispersive electrode connection or cardiac stimulation electrodeconnection, respectively. Electrosurgical generators are commonlyavailable and known to those skilled in the art, such as devicesmarketed by Birtcher Medical Systems. Inc. Of Irvine, Calif. USA; AspenSurgical Systems, Inc. Of Utica, N.Y. USA; and Valleylab, Inc. OfBoulder, Colo. USA. Cardiac stimulation devices for cardioversion,external pacing, and defibrillation are commonly available and known tothose skilled in the art, such as devices marketed by Hewlett-PackardCorporation of McMinnville, Oreg. USA, Zoll Medical Corporation ofNewton, Mass. USA and Physiocontrol Corporation of Redmond, Wash. USA.

Embodiments of the invention have been described. The claims follow.

What is claimed is:
 1. A biomedical electrode comprising: (a) a backingmaterial coated on a first side with a pressure-sensitive adhesive andhaving a non-adhesive margin to facilitate the handling of theelectrode; (b) a connector stud located in the backing material, thestud having an electrode plate located on the first side of the backingmaterial for electrical connection to the skin of a patient and, on asecond side of the backing material, a head portion to which anelectrical connector can be attached; (c) a strip ofionically-conductive adhesive extending, generally parallel to thenon-adhesive margin, across the adhesive-coated first side of thebacking material from edge to edge and over the electrode plate of thestud; and (d) a parallel strip of scrim material located at theinterface of the ionically-conductive and pressure-sensitive adhesive,the strip of scrim material being displaced, relative to the electrodeplate of the stud, towards the non-adhesive margin of the backingmaterial, and the edges of both strips nearest to the non-adhesivemargin being positioned to one side of the electrode plate. 2.biomedical electrode as claimed in claim 1, in which the edges of thestrips of scrim material and ionically-conductive material nearest tothe non-adhesive margin of the backing material are substantiallycontiguous.
 3. A method of manufacturing a biomedical electrode,comprising: providing a connector stud comprising an electrode plate forelectrical connection to the skin of a patient and a head portion;inserting the connector stud into a pierced opening in a backingmaterial, to locate the stud in the backing material with the electrodeplate and the head portion on opposite sides of the material; andproviding a strip of scrim material located to one side of the center ofthe electrode plate of the stud on a first side of the backing material.4. A method as claimed in claim 3, including the step of holding thepierced opening in an open condition while the stud is being inserted.5. A method of manufacturing a biomedical electrode, comprising: formingan opening in a backing material; inserting a tubular member through theopening from one side of the backing material; providing a connectorstud comprising an electrode plate for electrical connection to the skinof a patient, and a head portion; locating the stud, head portion first,in the end of the tubular member from the other side of the backingmaterial; and providing a strip of scrim material located to one side ofthe center of the electrode plate of the stud on a first side of thebacking material.
 6. A method as claimed in claim 5, in which theopening is a punched opening.
 7. A biomedical electrode comprising: abacking material coated on a first side with a pressure-sensitiveadhesive and having a non-adhesive margin to facilitate the handling ofthe electrode; a connector stud located in the backing material, thestud having an electrode plate located on the first side of the backingmaterial for electrical connection to the skin of a patient and, on asecond side of the backing material, a head portion to which anelectrical connector can be attached; a strip of ionically-conductiveadhesive extending, generally parallel to the non-adhesive margin,across the adhesive-coated first side of the backing material and overthe electrode plate of the stud, wherein the strip ofionically-conductive material is displaced, relative to the electrodeplate of the stud, towards the non-adhesive margin of the backingmaterial; and a parallel strip of scrim material located at theinterface of the ionically-conductive and pressure-sensitive adhesive,the strip of scrim material being displaced, relative to the electrodeplate of the stud, towards the non-adhesive margin of the backingmaterial, and the edges of both strips nearest to the non-adhesivemargin being positioned to one side of the electrode plate.
 8. Abiomedical electrode as claimed in claim 7, in which the edges of thestrips of scrim material and ionically-conductive material nearest tothe non-adhesive margin of the backing material are substantiallycontiguous.
 9. A biomedical electrode as claimed in claim 7, in whichthe strip of scrim material is located to one side of the center of theelectrode plate of the stud.
 10. A biomedical electrode as claimed inclaim 9, in which the strip of scrim material is located to one side ofthe electrode plate of the stud.
 11. A biomedical electrode as claimedin claim 7, in which the strip of scrim material extends between thepressure-sensitive adhesive and the electrode plate of the stud.
 12. Abiomedical electrode as claimed in claim 11, in which the width of thestrip of ionically-conductive adhesive is such that the adhesive coversthe electrode plate of the stud but does not extend substantially beyondthe electrode plate at the edge remote from the non-adhesive margin ofthe backing material.
 13. A biomedical electrode as claimed in claim 12,in which the strips of adhesive and scrim material are substantiallyco-extensive.
 14. A biomedical electrode as claimed in claim 13, inwhich the backing material is substantially rectangular in shape and hasthe non-adhesive margin along one side, the strips of scrim material andionically-conductive adhesive extending across the backing materialsubstantially parallel to the non-adhesive margin.
 15. A biomedicalelectrode as claimed in claim 14, in which the scrim material islaminated to the pressure-sensitive adhesive on the backing material.16. A biomedical electrode as claimed in claim 15, in which theionically-conductive adhesive is in the form of a pre-cured strip whichis laminated to the scrim and backing materials and to the electrodeplate.
 17. A biomedical electrode as claimed in claim 16, in which theconnector stud is a one-piece stud and is located in a pierced hole inthe backing material.
 18. A biomedical electrode as claimed in claim 17,in which the adhesive-carrying side of the electrode is covered by aremovable liner.
 19. A biomedical electrode comprising: a backingmaterial coated on a first side with a pressure-sensitive adhesive andhaving a non-adhesive margin to facilitate the handling of theelectrode; a connector stud located in the backing material, the studhaving an electrode plate located on the first side of the backingmaterial for electrical connection to the skin of a patient and, on asecond side of the backing material, a head portion to which anelectrical connector can be attached; a strip of ionically-conductive-adhesive-extending, generally parallel to the non-adhesive margin,across the adhesive-coated first side of the backing material and overthe electrode plate of the stud; and a parallel strip of scrim materiallocated at the interface of the ionically-conductive andpressure-sensitive adhesive, wherein the strip of scrim material isdisplaced, relative to the electrode plate of the stud, towards thenon-adhesive margin of the backing material, wherein the edges of bothstrips nearest to the non-adhesive margin are positioned to one side ofthe electrode plate, and further wherein the strip of scrim material islocated to one side of the center of the electrode plate of the stud.20. A biomedical electrode as claimed in claim 19, in which the edges ofthe strips of scrim material and ionically-conductive material nearestto the non-adhesive margin of the backing material are substantiallycontiguous.
 21. A biomedical electrode as claimed in claim 19, in whichthe strip of scrim material is located to one side of the electrodeplate of the stud.
 22. A biomedical electrode comprising: a backingmaterial coated on a first side with a pressure-sensitive adhesive andhaving a non-adhesive margin to facilitate the handling of theelectrode; a connector stud located in the backing material, the studhaving an electrode plate located on the first side of the backingmaterial for electrical connection to the skin of a patient and, on asecond side of the backing material, a head portion to which anelectrical connector can be attached; a strip of ionically-conductiveadhesive extending, generally parallel to the non-adhesive margin,across the adhesive-coated first side of the backing material and overthe electrode plate of the stud; and a parallel strip of scrim materiallocated at the interface of the ionically-conductive andpressure-sensitive adhesive, wherein the strip of scrim material isdisplaced, relative to the electrode plate of the stud, towards thenon-adhesive margin of the backing material, wherein the edges of bothstrips nearest to the non-adhesive margin being positioned to one sideof the electrode plate, and further wherein the strip of scrim materialextends between the pressure-sensitive adhesive and the electrode plateof the stud.
 23. A biomedical electrode as claimed in claim 22, in whichthe width of the strip of ionically-conductive adhesive is such that theadhesive covers the electrode plate of the stud but does not extendsubstantially beyond the electrode plate at the edge remote from thenon-adhesive margin of the backing material.
 24. A biomedical electrodeas claimed in claim 23, in which the strips of adhesive and scrimmaterial are substantially co-extensive.
 25. A biomedical electrode asclaimed in claim 24, in which the backing material is substantiallyrectangular in shape and has the non-adhesive margin along one side, thestrips of scrim material and ionically-conductive adhesive extendingacross the backing material substantially parallel to the non-adhesivemargin.
 26. A biomedical electrode as claimed in claim 25, in which thescrim material is laminated to the pressure-sensitive adhesive on thebacking material.
 27. A biomedical electrode as claimed in claim 26, inwhich the ionically-conductive adhesive is in the form of a pre-curedstrip which is laminated to the scrim and backing materials and to theelectrode plate.
 28. A biomedical electrode as claimed in claim 27, inwhich the connector stud is a one-piece stud and is located in a piercedhole in the backing material.
 29. A biomedical electrode as claimed inclaim 28, in which the adhesive-carrying side of the electrode iscovered by a removable liner.